1. Field of the Invention
This invention relates to a scanning system which transfers an image from a scanner over a network to a client computer. The invention is more particularly related to a system which allows a client computer to control a scanner connected to a network and receive images from the scanner over the network in a manner which emulates a direct connection of the scanner to the client computer. The invention is still further related to transferring an image from a scanner connected to a scanner server to a client computer over a network without the intermediate step of storing an image file on a file server.
2. Discussion of the Background
With the increasing familiarity of business people with computers, more computer based tasks are being performed by more people in office environments. Image scanners are becoming a more popular device in office environments both for enabling images to be included into documents and also to obtain images of documents in order to perform optical character recognition.
Heavy users of scanning devices usually have the luxury of ready access to a scanner. However, many people who use image scanners on an infrequent basis do not have the luxury of being able to directly scan an image into an application program running on their own computer. In the situation where the user does not have his own scanner, the user must go to a scanner and generate a file containing the image. This image file can then be copied to a floppy disk and walked to the user""s computer. The user""s computer then reads this disk in order to process the image file. However, depending on the resolution of the scanned image, the image file may be extremely large, thus making it inconvenient for the user to copy the image file to a floppy disk and then transfer the image file on the floppy disk to the user""s computer.
In an attempt to overcome this xe2x80x9csneaker networkxe2x80x9d concept of transferring images in which the user must physically carry the image on a storage medium from one computer to another, Hewlett-Packard has developed the HP scanjet 4si which allows a scanner to obtain an image file and the image file is subsequently written to a network file server. The image is stored on the file server, for example in a computer mailbox. After the image file is stored on the file server, the file can be retrieved and transferred over a computer network to the local hard disk or other storage device within the user""s computer, referred to as a client computer.
Disadvantages of this conventional system include the need of a separate file server and an intermediate storage of the file on the file server which is different from the final destination of the file. Further, there is no direct control of the scanner by the client computer nor can an application directly input the image file from the scanner. Therefore, conventional solutions to sharing a scanner among a plurality of users have their drawbacks and are not very convenient for the users of the shared scanner.
Accordingly, it is an object of this invention to provide a network scanning system which allows the transfer of image information from a scanner to a client computer over a computer network. It is a further object of the invention to provide a network scanning system which allows the transfer of image information from a scanner to a local computer without the need to first store the image on a network file server.
It is another object of the invention to provide a network scanning system which allows an application program running on a client computer to control and receive information from an image scanner over a computer network, in a manner which is similar to having the scanner directly connected to the client computer.
It is still another object of the invention to provide a network image scanning system which allows an image file to be transferred from a scanner server having the scanner connected thereto to the client computer, without having the image file stored on a separate file server.
These and other objects are accomplished by a network image scanning system which includes a client computer and a scanner server computer connected by a network, the server computer having the scanner connected thereto. According to a first aspect of the invention, a virtual TWAIN driver is utilized by an application program running in the client computer. The virtual TWAIN driver allows the application program to act, to a certain extent, as if the client computer is directly connected to an image scanner, even though the scanner is connected to a scanner server, the scanner server being connected to the client computer over a computer network. The virtual TWAIN driver interfaces with a client protocol encoder/decoder within the client computer. Commands and information are communicated over the computer network between the client and scanner server.
Within the scanner server, there is a server protocol encoder/decoder which is utilized to receive and transmit commands and information including image files and image information to the client computer. The scanner server includes an application program which interfaces between the server protocol encoder/decoder and a TWAIN driver. The TWAIN driver communicates with a scanner, such as a SCSI scanner, through a SCSI interface within the scanner server and an SCSI bus.
In order to properly communicate commands and information including control information and image information between the client computer running the application software and the scanner server computer, commands and data are communicated between the client computer and scanner server computer in accordance with a protocol utilized by the invention. The invention includes the commands and packet structure which are communicated between the client computer and scanner server.
Whenever there is an open communication session between the client computer and scanner server, an entry describing connection information is created in a process ID table which is stored in the scanner server computer. For the scan-to-application aspect of this invention, a table is utilized within the scanner server computer which includes information about the client computer and the executing process such as the thread ID, the machine name, the client address, the image file name, and scanning parameters.
Because the invention allows a device on a network to control and communicate with an application program running on the client computer and because the scanner server is able to write information to a local disk of the client computer, security of the client computer is a concern. The security concern is solved by the use of the commands utilized by the invention which are encoded into network packets. Most of these commands originate from the client computer and therefore, are assumed to be authorized by the client computer, thus preventing security problems. The commands which do not originate from the client computer originate from the host computer after the user, or software, has taken steps to register the client computer with the scanner server. In this manner, the client computer will only accept the commands (and accompanying data) prom the scanner server after the client computer has performed a registration process with the scanner server. The commands utilized by the scan-to-application aspect of this invention include open session, close session, read scanner parameters, set parameters, terminate scanner job, and read file, each of which originates from the client computer. The commands further include corresponding acknowledgements which are transmitted from the scanner server to the client computer.
In accordance with a second aspect of this invention, referred to as the scan-to-file operation, instead of transferring image information from the scanner server to an application program running in the client computer, an image file is transferred from the scanner server to a storage medium of the client computer. The client computer can then access this image file which is locally stored or stored on a medium which is locally mapped as a network drive by any type of image processing software or can simply store or further transfer the image file.
In the scan-to-file aspect of this invention, there is a file storage medium within the client computer, a client protocol encoder/decoder which encodes and decodes commands and information transmitted between the client and server, and a program called a file catcher which registers the client computer with the server so that the server will be able to transmit files to the client computer, and also controls the receiving and storage of image files. The scanner server is connected to the client computer by any type of network and includes a server protocol encoder/decoder, scan task software which controls the operations of the scanner connected to the scanner server, a TWAIN driver and a scanner interface.
The scan-to-file aspect of this invention operates by first registering the client computer with the scanner server. The user can then go to the scanner server and select the client computer which is to receive the generated image file. An image is scanned at the scanner which is connected to the scanner server and the image file is transmitted to the client to the computer. When the client computer receives the file, the file is stored on a local storage medium of the client computer.
The scanner server includes a table which registers active processes between the client and scanner server and also includes a table which registers machines to which image files can be transferred. The table listing the available machines is called the machine name table and contains an index, a machine name field, and a client address field for each entry. As with the scan-to-application aspect of this invention, special network scanning commands are transmitted between the client and server for the scan-to-file operation including the open and close session commands, an initialize session command, a terminate session command, and corresponding acknowledge commands. Another scan-to-file command, the read file command, is transmitted from the scanner server to the client computer in order to transfer the image file to the local computer. There is also a corresponding acknowledge command transmitted from the client computer to the scanner server.